1. Field of the Invention
The present invention relates to a semiconductor device and an information processing apparatus including the same, and more particularly relates to a semiconductor device that generates an internal power potential stepped up by a charge pump operation and an information processing apparatus including the same.
2. Description of Related Art
In most semiconductor devices, an internal voltage is used which is different from an external voltage supplied from the outside. In this case, an internal-voltage generation circuit that generates the internal voltage different from the external voltage is provided in the semiconductor device. For example, when an internal voltage to be generated is higher than an external voltage, the internal-voltage generation circuit steps up the external voltage to generate the internal voltage.
In recent years, an effort to lower the external voltage has been made in order to reduce current consumption. Meanwhile, because some circuit blocks in the semiconductor device require a high internal voltage that is difficult to be lowered, a step-up level by the internal-voltage generation circuit is likely to increase. To obtain the high internal voltage, it is necessary to step up the external voltage three or more times by using a plurality of pumping circuits. This causes a problem that a circuit dimension of the internal-voltage generation circuit is increased.
Japanese Patent Application Laid-Open No. 2004-319011 discloses a semiconductor device in which a dedicated external power-supply terminal is provided in a step-up power-supply circuit. A dedicated external voltage VDD3 is supplied to the external power-supply terminal, which is different from external voltages VDDM and VDDL that are supplied to a memory circuit and a logic circuit.
In the semiconductor device described in Japanese Patent Application Laid-Open No. 2004-319011, because a charge pump operation is performed by using the dedicated external voltage VDD3, efficient step-up can be performed. However, in the disclosure of Japanese Patent Application Laid-Open No. 2004-319011, both an amplitude of a clock signal supplied to one of electrodes of a capacitor and a voltage for pre-charging the other electrode of the capacitor are the same as the dedicated external voltage VDD3, and accordingly a level of a generated step-up voltage VPP is theoretically two times the external voltage VDD3. Therefore, when the external voltage VDD3 has a level close to the level of the step-up voltage VPP, the step-up level becomes too high, so that not only it is hard to perform a stable charge pump operation but also it causes a problem of increasing the current consumption.